Ultra short wave system for twoway communication



' Aug. 29,1939.

KRIEBEL 2,1 71,2 18

ULTRA SHORT WAVE SYSTEM FOR TWO-WAY COMMUNICATION Filed July 6, 1938 VERTICAL ANTEIVA/A ORIENT/mu LOOP AfiJTfMVA DIRECTIVE V 7 AWE/m4 (A 5 ,53

V r L 01m b'l6/I I I m aumcy 0SCILLATOR MIXER (kso l j Irma/2150mm DETECTOR 4110/0 FREQl/l-WCY l-kEflI/l-WCY AMPl/HER AMPLIFIER lNVENTOR WAL TER KRIEBEL ATTORNEYS was creme caries stares ULTRA SHORT WAVE SYSTEM FOR TWO- WAY COMMUNICATION Walter Kriebel, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Eclegraphic in. b. li-L, Berlin, Germany, a corporation of Germany Application July 6, 1938, Serial- No. 217,684 In Germany June 24, 1937 6 Claims. (01. 250-9) The present invention is concerned with an art. In the present connection, however, there arrangement for two-way communication on is an added advantage in that some unauthorized short and ultra-short waves for installations station, which may accidentally have picked up comprising at least one mobile station, and for the call and which happens to have its receiver the use of which the location of the correspondtuned to the calling wave, will probably be un- 5 ant station must be ascertained prior to actual able to listen in on the conversation for the signal transmission. reason that it is not tuned to the other wave,

The locating and the calling of a mobile staand it may not be located in the sector of the tion which works with directional or beam radisharply focussed beam.

10 ators for sending and reception is very difiicult The chances of unauthorized persons listening 10 the absence of optical visibility, that is, at in may be diminished still further, while at the night time and in foggy weather. same time a technical advantage is secured, by

It has already been suggested in the prior art resorting to heterodyne reception, and by suitto furnish beam equipment for this purpose with able choice of carrier frequencies used in the two means adapted to enlarge and widen the apercorresponding stations so that they differ a 18 tural angle. However, it has been found that definite amount, that is, the amount of the even by steps of this kind the problem in quesintermediate frequency wave. The identical step tion can not always be solved in a satisfactory may be adopted for the oscillator tubes of the manner, least of all when two mobile stations transmitting portion of the equipment.

20 alter their positions all the time and in an un- As a matter of economy and simplicity of 20 controllable or unforeseeable manner, as, for equipment, the frequencies of the oscillators at instance, in making expeditions. Directional the two stations can be so chosen that the same radiators in order to locate the correspondent beat frequency is always produced by heterodynstation must, therefore, be turned. It may then ingthe received wave with the output of the 26 happen quite easily that both stations rotate local oscillator. Hence one fixedly tuned inter- 5 their directional radiators just at such a rate mediate frequency amplifier at each station is and rhythm that their directional characteristics suflicient for the ultra-short wave reception as can not come to register. The arrangement and well as for reception of the longer calling wave. working scheme here disclosed is designed to My invention will now be described in more 30 remedy this condition. Moreover, the present detail, reference being made to the accompany- 30 invention discloses ways and means adapted to ing drawing in which the sole figure thereof maintain a signal communication or connection represents schematically a preferred arrangeonce it has been established, and further to prement of components of a transmitting and reclude listening in by unauthorized parties or at ceiving station, which components are essential 85 least to make such an attempt more diiiicult. to the successful operation of the device.

The duplex or two-way communication sys- For signal transmission an ultra-short wave tem here disclosed comprises short or ultra-short directional antenna 1 is provided. The antenna wave equipment operating between two stations, system preferably includes a plurality of dipoles one at least of which is a mobile station. Since disposed in a plane. The energy radiated by the directional beams are employed, the position of antenna may be sharply focussed in a beam by 40 the corr spondent has to be determined prior to means of a reflector 2. the actual transmission of ultra-short wave sig- The radio apparatus unit 4 is designed for twonals. For purposes of orientation, therefore, I way communication and has leads 3 interconhave found it to be a convenience to radiate necting this unit with. the antenna system i.

longer waves from each of two omni-directional The unit 6 includes an oscillator which gener- 45 antennae located at stations between which a ates the energy to be transmitted and which short wave two-way communication is to be during reception serves for heterodyning with established. This longer wave is picked up at the incoming energy. Preferably the oscillator the receiving end by a directional antenna argenerates a wave of approximately cm. The

50 rangement. The signals so received serve to outgoing signal may be modulated by means of 50 orient the beam antenna both for transmission a modulator 5, while the incoming energy upon and reception of ultra-short wave signals. heterodyning with the output of the oscillator 4 The idea of utilizing two dissimilar waves one to produce an intermediate frequency, may be for calling and the other for transmission of a fed across the switch 6 to an intermediate fremessage is fundamentally known in the prior quency amplifier unit I. .This amplifier unit 55 may consist, for example, of three stages. The output from the amplifier is then fed to a detector 8 and finally through an audio frequency amplifier 9 to any suitable responsive device such as a telephone instrument I0.

To locate the position of and to call a correspondent station, another radio frequency unit II i provided which works, for instance, on a 4-meter wave length. The call wave is sent out non-directionally, assuming that the location of the desired correspondent station is unknown. The calling wave is produced by an oscillator which is comprised in the unit I I, and is sent out, for example, by way of a vertical rod-type antenna l2. To locate an answering station, a small directional antenna I3 is provided, say, in the form of a frame or loop. If desired, for the locating of a correspondent station, the vertical antenna [2 and the loop antenna I3 may be made to act conjointly and simultaneously. What then results is an unilaterally directional field strength characteristic or cardioid. The call oscillator of the unit II furnishes oscillations as also required for forming'the intermediate frequency which is fed to a receiver by way of a switch I4. As above pointed out it is advisable to choose a frequency difference between the signal waves and the call waves such that in either case the same intermediate frequency will be obtained. If this condition is satisfied then an allpurpose receiver and amplifier may be employed for reception. Inasmuch as the efficiency of a long-wave system, say, Working with 4-meter waves, is greater than that of an ultra-short-wave system, it will be seen that in a great many instances the intermediate frequency gain that is necessary in the call part of the equipment may be smaller. Hence the 4-meter wave receiving unit H is connected only to the second or the third stage of the intermediate frequency amplifier l. The preceding stages of the intermediate frequency amplifier may be disconnected at will in order that the batteries of the equipment may be relieved of load during the call and search period.

The'modulator means 5 may be separate or joint. In order to insure rapid change-over of connections of the radio frequency units 4 and l 1 during the process of orienting the ultra-shortwave antenna I, it may be advantageous to interlock the change-over switches 6 and [4 so that one switch closes as the other opens. In many instances it will be found to be difficult in the first setting of the directional antennae to orient them toward the correspondent station with exactness. In fact, to insure this condition it will prove necessary to change several times from call to signal wave in order that the correspondent station may be given suitable instructions.

The inter-lock between the switches 6 and I4 offers the folowing further advantage:

If for one reason or another the ultra-shortwave receiver fails or the signal is disturbed for some extraneous cause, it is possible imediately to switch over to the call or ringing wave and to continue intelligence transmission on this wave or at least to advise the oposite station that there is trouble. Also in such a case it will again be found especially convenient to adopt a single intermediate frequency amplifier which is tuned to a frequency obtainable by heterodyning with either of the two carier waves.

The details of suitable circuit arrangements for enabling the unit 4 to be used alternatively for transmission and reception have not been shown since devices of this sort are well known in the art. For example, United States Patent No. 1,598,26 to Paul Ware shows one such duplex system as applied to radio telegraphy.

It wil be understood that the idea underlying the present invention is not confined to the exemplified embodiment as herein described, nor do the exact details as shown in the appended drawing need to be followed by those skilled in the art.

I claim:

1. A system for radio communication between two stations, one of said stations comprising two carrier Wave generators, modulation mixer means operatively associated with each of said generators, means including an omni-directional antenna connected to one of said generators for radiating a call-signal wave, means including a second antenna connected to the other of said generators for radiatingin any desired direction a focussed beam of ultra-high frequency signalling energy, means in circuit with each of said mixer means for modulating the output energies of their associated generators, means including an orientable directional antenna in cooperation with said omni-directional antenna for obtaining an indication of the direction in which the other station lies, means for enabling said generators and said mixer means to deliver a common intermediate frequency output by heterodyning with incoming waves of two different frequencies, receiving apparatus comprising an amplifier tuned'to said common intermediate frequency, a detector, an audi frequency amplifier and a responsive device, all serially connected to said intermediate frequency amplifier, and means for connecting said intermediate frequency amplifier alternatively to the generator-mixer means associated with said second antenna or to the combination of omni-directional and orientable antennae.

2. A system for duplex radio communication comprising radio frequency transmitting and receiving equipment disposed at each of two stations one at least of said stations being a mobile station the position of which is to be determined at the other of said stations prior to the trans mission of traflic signals therebetween, each of said stations comprising omni-directional and orientable antennae and a combining circuit connected to said antennae and suitably arranged for obtaining an indication of the direction in which a call-signal initiated by the other station is brought in, each of said stations comprising further an ultra-short wave directive beam antenna and ultra-short wave transmitting and receiving apparatus operatively associated therewith, "an intermediate frequency amplifier, switching means for connecting said amplifier alternatively to said ultra-short wave apparatus or to the'combining circuit of the other two antennae, and apparatus for deriving an intelligible response from said intermediate frequency amplifier. V r

'3. A system in accordance with claim 2 and. further characterized in. that said combining circuit associated with the omni-directio'nal and orientable antennae includes oscillator means for delivering signalling energy to be modulated and transmitted, said oscillator means being further adapted to heterodyne with an incoming signal whereby said combining circuit is enabled to produce an intermediate frequency acceptable to said intermediate frequency amplifier.

4. A system in accordance with claim 2 and said ultra-high frequency apparatus and at least one of said stages being connectable to the combining circuit which is associated with said omnidirectional and orientable antennae.

6. A system in accordance with claim 2 and having interlocking switching means for obtaining the alternative connections of said intermediate frequency amplifier with said ultra-high frequency apparatus and with said combining circuit, respectively.

WALTER KRIEBEL. 

